标题： GJ 238 b：围绕15.2秒差距处的M2.5矮星运行的0.57倍地球半径行星 显示英文标题

标题： GJ 238 b: A 0.57 Earth Radius Planet Orbiting an M2.5 Dwarf Star at 15.2 pc

摘要： 我们报告发现了一颗凌日行星 GJ 238 b，其半径为$0.566\pm0.014$ R$_{\oplus}$ （$1.064\pm0.026$ 倍于火星的半径），轨道周期为 1.74 天。 凌日信号由 TESS 任务检测并指定为 TOI-486.01。 恒星的位置接近南黄道极，使其在 TESS 观测南天时能够几乎连续观测。 恒星主机是一个M2.5矮星，有$V=11.57\pm0.02$ mag，$K=7.030\pm0.023$ mag，距离为$15.2156\pm0.0030$ pc，质量为$0.4193_{-0.0098}^{+0.0095}$ M$_{\odot}$，半径为$0.4314_{-0.0071}^{+0.0075}$ R$_{\odot}$，有效温度为$3{,}485\pm140$ K。我们通过排除或使每个假阳性情景极不可能，基于档案数据和地面后续观测来验证行星候选者。 验证由于恒星的较小尺寸和较高的自行运动而得到促进，为$892.633\pm0.025$毫角秒年$^{-1}$。 显示英文摘要

摘要： We report the discovery of the transiting planet GJ 238 b, with a radius of $0.566\pm0.014$ R$_{\oplus}$ ($1.064\pm0.026$ times the radius of Mars) and an orbital period of 1.74 day. The transit signal was detected by the TESS mission and designated TOI-486.01. The star's position close to the Southern ecliptic pole allows for almost continuous observations by TESS when it is observing the Southern sky. The host star is an M2.5 dwarf with $V=11.57\pm0.02$ mag, $K=7.030\pm0.023$ mag, a distance of $15.2156\pm0.0030$ pc, a mass of $0.4193_{-0.0098}^{+0.0095}$ M$_{\odot}$, a radius of $0.4314_{-0.0071}^{+0.0075}$ R$_{\odot}$, and an effective temperature of $3{,}485\pm140$ K. We validate the planet candidate by ruling out or rendering highly unlikely each of the false positive scenarios, based on archival data and ground-based follow-up observations. Validation was facilitated by the host star's small size and high proper motion, of $892.633\pm0.025$ mas yr$^{-1}$.